diff --git a/tb/pcs.py b/tb/pcs.py
index 7e6c280..27b32c3 100644
--- a/tb/pcs.py
+++ b/tb/pcs.py
@@ -7,10 +7,11 @@ import itertools
 
 import cocotb
 from cocotb.clock import Clock
+from cocotb.regression import TestFactory
 from cocotb.triggers import ClockCycles, Edge, RisingEdge, FallingEdge, Timer
 from cocotb.types import LogicArray
 
-from .util import alist, classproperty, ReverseList
+from .util import alist, classproperty, ReverseList, timeout
 
 class Code(enum.Enum):
     _0 = (0b11110, '0')
@@ -194,14 +195,34 @@ async def pcs_recv_packet(pcs):
         yield code.data
     raise PrematureEndError()
 
-async def pcs_send_codes(pcs, codes):
+def one_valid():
+    return 1
+
+def two_valid():
+    return 2
+
+def rand_valid():
+    return random.randrange(3)
+
+class saw_valid:
+    def __init__(self):
+        self.last = 0
+        # Lie for TestFactory
+        self.__qualname__ = self.__class__.__qualname__
+
+    def __call__(self):
+        self.last += 1
+        if self.last > 2:
+            self.last = 0
+        return self.last
+
+async def pcs_send_codes(pcs, codes, valids):
     await FallingEdge(pcs.rx_clk)
     codes = list(codes)
     bits = itertools.chain(*codes)
     try:
         while True:
-            #valid = 2
-            valid = random.randrange(3)
+            valid = valids()
             pcs.pma_data_rx_valid.value = valid
             if valid == 0:
                 data = 'XX'
@@ -254,8 +275,8 @@ async def test_tx(pcs):
     await cocotb.start(mii_send_packet(pcs, [0x5, None]))
     assert [0x5, 0x5, None] == await alist(pcs_recv_packet(pcs))
 
-@cocotb.test(timeout_time=10, timeout_unit='us')
-async def test_rx(pcs):
+@timeout(10, 'us')
+async def test_rx(pcs, valids):
     pcs.pma_data_rx.value = LogicArray('11')
     pcs.pma_data_rx_valid.value = 2
     pcs.link_status.value = 1
@@ -276,7 +297,7 @@ async def test_rx(pcs):
         (Code('J'), Code('K'), Code('I'), Code('I'), (1,1)),
         # Packet spacing
         *((*frame([0x55, 0x55]), (1,) * i) for i in range(10))
-    )))
+    ), valids))
 
     assert packet == await alist(mii_recv_packet(pcs))
 
@@ -291,3 +312,7 @@ async def test_rx(pcs):
     # Test packet spacing
     for _ in range(10):
         assert [0x5, 0x5] == await alist(mii_recv_packet(pcs))
+
+rx_tests = TestFactory(test_rx)
+rx_tests.add_option('valids', (one_valid, two_valid, rand_valid, saw_valid()))
+rx_tests.generate_tests()
diff --git a/tb/pmd.py b/tb/pmd.py
index a3a4baf..86a3d52 100644
--- a/tb/pmd.py
+++ b/tb/pmd.py
@@ -4,13 +4,30 @@ from statistics import NormalDist
 import cocotb
 from cocotb.binary import BinaryValue
 from cocotb.clock import Clock
+from cocotb.regression import TestFactory
 from cocotb.triggers import RisingEdge, Timer
 
+from .util import timeout
+
 def print_list_at(l, i):
     print(' ' * max(50 - i, 0), *l[max(i - 50, 0):i+50], sep='')
 
-@cocotb.test(timeout_time=100, timeout_unit='us')
-async def test_rx(pmd):
+BITS = 1000
+
+def random_delays(count):
+    # Target BER is 1e9 and the maximum jitter is 1.4ns
+    # This is just random jitter (not DDJ or DCJ) but it'll do
+    delay_dist = NormalDist(8000, 1400 / NormalDist().inv_cdf(1-2e-9))
+    return (int(delay) for delay in delay_dist.samples(count))
+
+def mindelays(count):
+    return (7900,) * count
+
+def maxdelays(count):
+    return (8100,) * count
+
+@timeout(100, 'us')
+async def test_rx(pmd, delays):
     pmd.signal_detect.value = 0
     await Timer(1)
     await cocotb.start(Clock(pmd.rx_clk_125, 8, units='ns').start())
@@ -18,22 +35,18 @@ async def test_rx(pmd):
     await Timer(random.randrange(0, 8000), units='ps')
     await cocotb.start(Clock(pmd.rx_clk_250, 4, units='ns').start())
 
-    ins = [random.randrange(2) for _ in range(1000)]
+    ins = [random.randrange(2) for _ in range(BITS)]
     async def generate_bits():
         # random phase
         await Timer(random.randrange(0, 8000), units='ps')
         pmd.signal_detect.value = 1
-        # Target BER is 1e9 and the maximum jitter is 1.4ns
-        # This is just random jitter (not DDJ or DCJ) but it'll do
-        delay_dist = NormalDist(8000, 1400 / NormalDist().inv_cdf(1-2e-9))
-        for i, delay in zip(ins, (int(delay) for delay in delay_dist.samples(len(ins)))):
+        for i, delay in zip(ins, delays(len(ins))):
             pmd.rx.value = i
             try:
                 pmd.delay.value = delay
             except AttributeError:
                 pass
             await Timer(delay, units='ps')
-            #await Timer(8100, units='ps')
         pmd.signal_detect.value = 0
     await cocotb.start(generate_bits())
 
@@ -69,3 +82,7 @@ async def test_rx(pmd):
     # There will be a few bits at the end not recorded because signal_detect
     # isn't delayed like the data signals
     assert best_corr > len(ins) - best_off - 10
+
+rx_tests = TestFactory(test_rx)
+rx_tests.add_option('delays', (random_delays, mindelays, maxdelays))
+rx_tests.generate_tests()
diff --git a/tb/util.py b/tb/util.py
index 5f04e54..c009afe 100644
--- a/tb/util.py
+++ b/tb/util.py
@@ -1,6 +1,12 @@
 # SPDX-License-Identifier: AGPL-3.0-Only
 # Copyright (C) 2022 Sean Anderson <seanga2@gmail.com>
 
+import functools
+
+import cocotb
+from cocotb.triggers import with_timeout
+from cocotb.result import SimTimeoutError
+
 async def alist(xs):
     return [x async for x in xs]
 
@@ -9,6 +15,24 @@ class classproperty(property):
     def __get__(self, cls, owner):
         return classmethod(self.fget).__get__(None, owner)()
 
+class timeout:
+    def __init__(self, time, unit):
+        self.time = time
+        self.unit = unit
+
+    def __call__(self, f):
+        coro = cocotb.coroutine(f)
+
+        @functools.wraps(f)
+        async def wrapped(*args, **kwargs):
+            r = coro(*args, **kwargs)
+            try:
+                return await with_timeout(r, self.time, self.unit)
+            except SimTimeoutError:
+                r.kill()
+                raise
+        return wrapped
+
 class ReverseList(list):
     def __init__(self, iterable=None):
         super().__init__(reversed(iterable) if iterable is not None else None)